Trees have been used as building materials since the beginning of humanity and construction. But since the period of industrialization, concrete and steel have taken over the tree-wood as building materials. Owing to the negative impacts of the use of concrete and steel on the environment, the focus has turned to a more sustainable material. However, the timber obtained from wood that had a bad reputation for being ignitable has given rise to an alternative material known as Laminated timbers.
Production Of Laminated Timbers
Laminated timbers are used all over the world and majorly in the European countries and are produced from hardwood. The wood is trimmed, smoothed, and is kiln-dried to reduce the moisture content to an extent that it does not allow for cracking and change in dimensions. The lumber is then stacked one above the other to form a single piece and glued to each other with an environmentally– friendly adhesive. The lumbers are selected and arranged considering the grains and defects of the wood to attain maximum structural integrity. The pieces are then hydraulically pressed to achieve the required strength. The laminated pieces are connected using bolts or steel dowels and steel plates during construction.
Laminated timbers are manufactured in two ways:
- Glued laminated timber
- Cross-laminated timber
1. Glued laminated timber
Glued laminated timber or ‘glulam’ is made of multiple layers of solid wood lumbers glued to each other with adhesives to form a single piece. These pieces are oriented in one direction which appears as a solid piece of wood. This can result in shrinkage or expansion of length like solid wood. The pieces of glued laminated timber are generally used as a structural frame of the building, i.e., as beams and columns, and also for domes and vaults. As glulam is made by joining the pieces of wood, it can be manufactured in a variety of sizes and shapes and span large areas as a single piece. It can also be molded into curved forms. It is used as the main material in various typologies of buildings including industrial structures, sports halls, and commercial buildings, as well as in bridges.
2. Cross-laminated timber
Cross-laminated timber or ‘CLT’ is the same as glulam except that it differs in the arrangement of wood pieces. In this, the wood pieces do not go in one single direction, rather they are glued perpendicular at each layer to form the single piece. Because of this, the piece becomes structurally more rigid. This does not allow for shrinkage in length and width. Like glulam, cross-laminated timber is also used for various building typologies. The strength it gets due to the perpendicular arrangement of wood pieces has proved efficient for use even in high-rise buildings. An example of this is an 18-storeyed mixed-use building, Mjøstårnet, in Norway.
Both ways have proven this material efficient in terms of strength, versatility, and high speed. It is also a lighter material than steel and concrete. But in both cases, high precision in sizes and shapes is required to be manufactured. This is done by using computer softwares. Handling of laminated timber should be done carefully as it is susceptible to scratches and damages during transportation. This causes a high risk as it might reduce its structural strength. Unless the pieces of laminated timber are intended for use in external areas exposed to weather, in which it is given weather protection treatment, it should be kept away from places where it is exposed to the weather.
Embodied Energy Of laminated Timber
Laminated timber is a preferred alternative to steel and concrete. According to studies, it takes three times more energy and twelve times more fossil fuels to produce steel structures than it takes to produce laminated timber structures. Laminated timber has much lower embodied energy than its steel and concrete counterparts. Since each piece is made from relatively small pieces of wood, it reduces the overall use of wood that is otherwise used as big pieces for construction. This lessens the reliance on large pieces of wood and so, reduces the cutting of trees drastically. Further, the gas emission is lower for laminated timbers so if they are burned when they get damaged after their life cycle is complete, more energy is recovered. Usage of environmentally friendly adhesive, too, plays an important part in the process.
A Mass Timber Revolution
Mass timber is an alternative to buildings made of steel and concrete. As we build new structures and occupy most of the natural land, not moving to timber construction and continuing with steel and concrete would be a disaster, as it will ultimately go into the landfill. But it is also important to produce timber from sustainable forestry. It should not be made at the expense of the natural forests.
Advantages Of Laminated Timbers
- It is an eco-friendly material that reduces carbon emissions. Trees or wood have carbon in them to an extent. This allows the construction to last for at least fifty years. Steel and concrete industries account for a large percentage of CO2 emissions. These emissions are avoided by the use of laminated timber. Also, trees absorb carbon dioxide and as laminated timber is a product of wood it does a similar performance, making it a sustainable material.
- It has excellent fire-resistant properties. Various studies have shown that laminated timbers pass the fire safety tests.
- It also has excellent earthquake resistant properties. Various tests have proven its strength to vibrations. Also, the damaged wood in extreme earthquakes can be recycled.
- This material can be grown in abundance considering the terms of sustainable forestry.
- It reduces construction time drastically. Tall buildings can be constructed within a few weeks. The sizes and shapes of laminated timber, if planned with high precision, also eliminate the material waste. It also results in lower construction costs.
- Laminated timbers are left exposed which gives buildings an aesthetically pleasing appearance.
Laminated timbers can be used as structural members, walls, floors, and roofs. It can also be used as curved beams, trusses, floor slabs in a variety of sizes and shapes and can be used both outdoors and indoors. Here are a few examples where it has been used-
1. Puukuokka Housing Block, Finland
2. Louis Vuitton Foundation, Paris for roof beams
3. The Smile Pavilion made using Cross-Laminated Timber
4. Sport Court in Sarcelles, France
5. Montmorency Forest Bridge